Background and Aims The concentration and composition of nitrogen (N) in must is critical to yeast fermentation and aroma profiles in wine. We investigated the effect of adding branched‐chain amino acids (BCAAs, including l‐valine, l‐leucine and l‐isoleucine) to a non‐limited N medium on the formation of aromatic compounds and on gene expression patterns of the wine yeast Saccharomyces cerevisiae. Methods and Results A synthetic N‐sufficient must was supplemented with BCAAs and fermented with S. cerevisiae. The fermentation kinetics, aroma characteristics and yeast global gene expression in wine with addition of BCAAs were compared with that of the Control. Addition of BCAAs improved yeast growth and fermentation activity, increased the production of higher alcohols, medium‐chain fatty acids and their corresponding esters (82, 34 and 49% increment compared to that of the Control, respectively). The comparative transcriptomic analysis revealed that 25 genes varied in their expression during fermentation with added BCAAs relative to that of the Control, which are mainly involved in yeast growth and proliferation (GIP1, DIT2, RCK1, SPO1 and MEK1) and transport of amino acids (GAP1). Conclusions An increase in BCAA transport ability and in yeast population is the main reason for achieving an increased concentration of volatile aroma compounds in wine with addition of BCAAs. Significance of the Study Our results suggest that adding BCAAs into N‐sufficient must is still an efficient way to adjust wine's aromatic composition and improve aroma complexity.

The effects of adding branched-chain amino acids (BCAAs, including L-valine, L-leucine and L-isoleucine), L-phenylalanine and a mixture of them (BCAAs + Phe) on the fermentation profiles of wine yeast EC1118 and the production of volatile compounds were investigated in synthetic grape juice. The addition of selected amino acids had no considerable influence on the yeast growth and primary metabolites of the sugars. Adding BCAAs increased the production of higher alcohols, medium-chain fatty acids (MCFAs) and their corresponding ethyl esters. In comparison, adding Phe promoted the production of 2-phenylethanol, 2-phenylethyl acetate and ethyl esters of MCFAs. Nevertheless, the supplementation of BCAAs + Phe further heightened the production of MCFAs, acetate esters and ethyl esters of MCFAs compared to the single additions, but it attenuated the production of various higher alcohols (1-propanol, 2,3-butanediol and methionol) compared to the addition of BCAAs, and of 2-phenylethanol and 2-phenylethyl acetate contents compared to the Phe addition. These results suggest that adding BCAAs or Phe is an efficient way to adjust wine's aromatic composition and complexity. Meanwhile, the combined addition of BCAAs + Phe could be a potential tool to further manipulate wine's aromatic profile by accentuating or suppressing the formation of certain aroma compounds.